数据结构 C 代码 2.4: 静态链表

摘要: 静态链表有助于理解操作系统空间分配机制, 遗憾的是, 多数人没写这个代码. 强烈建议硬杠一下. 毕竟这是学霸与学渣的重要分界线.

先上代码, 再说废话.

#include 
#include 

#define DEFAULT_SIZE 5

typedef struct StaticLinkedNode{
	char data;

	int next;
} *NodePtr;

typedef struct StaticLinkedList{
	NodePtr nodes;
	int* used;
} *ListPtr;


ListPtr initLinkedList(){
	// The pointer to the whole list space.
	ListPtr tempPtr = (ListPtr)malloc(sizeof(StaticLinkedList));

	// Allocate total space.
	tempPtr->nodes = (NodePtr)malloc(sizeof(struct StaticLinkedNode) * DEFAULT_SIZE);
	tempPtr->used = (int*)malloc(sizeof(int) * DEFAULT_SIZE);

	// The first node is the header.
	tempPtr->nodes[0].data = '';
	tempPtr->nodes[0].next = -1;

	// Only the first node is used.
	tempPtr->used[0] = 1;
	for (int i = 1; i < DEFAULT_SIZE; i ++){
		tempPtr->used[i] = 0;
	}// Of for i

	return tempPtr;
}// Of initLinkedList


void printList(ListPtr paraListPtr){
	int p = 0;
	while (p != -1) {
		printf("%c", paraListPtr->nodes[p].data);
		p = paraListPtr->nodes[p].next;
	}// Of while
	printf("rn");
}// Of printList


void insertElement(ListPtr paraListPtr, char paraChar, int paraPosition){
	int p, q, i;

	// Step 1. Search to the position.
	p = 0;
	for (i = 0; i < paraPosition; i ++) {
		p = paraListPtr->nodes[p].next;
		if (p == -1) {
			printf("The position %d is beyond the scope of the list.rn", paraPosition);
			return;
		}// Of if
	} // Of for i

	// Step 2. Construct a new node.
	for (i = 1; i < DEFAULT_SIZE; i ++){
		if (paraListPtr->used[i] == 0){
			// This is identical to malloc.
			printf("Space at %d allocated.rn", i);
			paraListPtr->used[i] = 1;
			q = i;
			break;
		}// Of if
	}// Of for i
	if (i == DEFAULT_SIZE){
		printf("No space.rn");
		return;
	}// Of if

	paraListPtr->nodes[q].data = paraChar;

	// Step 3. Now link.
	printf("linkingrn");
	paraListPtr->nodes[q].next = paraListPtr->nodes[p].next;
	paraListPtr->nodes[p].next = q;
}// Of insertElement


void deleteElement(ListPtr paraListPtr, char paraChar){
	int p, q;
	p = 0;
	while ((paraListPtr->nodes[p].next != -1) && (paraListPtr->nodes[paraListPtr->nodes[p].next].data != paraChar)){
		p = paraListPtr->nodes[p].next;
	}// Of while

	if (paraListPtr->nodes[p].next == -1) {
		printf("Cannot delete %crn", paraChar);
		return;
	}// Of if

	q = paraListPtr->nodes[p].next;
	paraListPtr->nodes[p].next = paraListPtr->nodes[paraListPtr->nodes[p].next].next;
	
	// This statement is identical to free(q)
	paraListPtr->used[q] = 0;
}// Of deleteElement


void appendInsertDeleteTest(){
	// Step 1. Initialize an empty list.
	ListPtr tempList = initLinkedList();
	printList(tempList);

	// Step 2. Add some characters.
	insertElement(tempList, 'H', 0);
	insertElement(tempList, 'e', 1);
	insertElement(tempList, 'l', 2);
	insertElement(tempList, 'l', 3);
	insertElement(tempList, 'o', 4);
	printList(tempList);

	// Step 3. Delete some characters (the first occurrence).
	printf("Deleting 'e'.rn");
	deleteElement(tempList, 'e');
	printf("Deleting 'a'.rn");
	deleteElement(tempList, 'a');
	printf("Deleting 'o'.rn");
	deleteElement(tempList, 'o');
	printList(tempList);

	insertElement(tempList, 'x', 1);
	printList(tempList);
}// Of appendInsertDeleteTest


void main(){
	appendInsertDeleteTest();
}// Of main

Space at 1 allocated.
linking
Space at 2 allocated.
linking
Space at 3 allocated.
linking
Space at 4 allocated.
linking
No space.
 Hell
Deleting 'e'.
Deleting 'a'.
Cannot delete a
Deleting 'o'.
Cannot delete o
 Hll
Space at 2 allocated.
linking
 Hxll
Press any key to continue

1. nodes 存储节点, used 存储空间使用情况, 0 表示空闲, 1 表示被占用.
2. next 是一个整数, 表示相对地址. 在操作系统中, 应该是绝对地址.
3. 这里用 -1 表示 NULL.
4. nodes[0] 永远存储头节点.
5. 并没考虑多个链表共享同一片空间的情况, 但这是真实操作系统需要面对的.
6. paraListPtr->nodes[paraListPtr->nodes[p].next].data 这种代码有一点点复杂, 懂了就好办. 这个代码的调拭也就 10 分钟.

欢迎留言讨论.